Epicyclic clock drive mechanism



May 25, 1965 G. W. I oHF ETAL 3,184,909

EPICYCLIC CLOCK DRIVE MECHANISM Filed oct. 5o, 1965 sheets-sheet 1 INVENTORS GERALD W. LOHF PHLP F.WALKER ALONZO RAY ELLSWORTH May 25, 1965 G. w. LoHF r-:TAL

EPICYGLC CLOCK DRIVE MECHANISM 5 Sheets-Sheet 3 Filed Oct. 50, 1963 INVENTORS GERALD W. LOHF PHLlP FWALKER ALQNZO RAY ELLSWORTH United States Patent O Sdddiw EPICYCLHC CLCK Dillvlil MEQHANESM Gerald W. lLohf, Milwaukee, Philip ld. i ether, wauwatosa, and Alonso Ray Eilswcrth, Milwaukee, Wis.,

assgnors to Allen-Eradiey Qompany, hdilwauhee-s a Wisconsin corporation Filed @en 3h, i963, Ser. No. 326,07) liti Claims. (Si. SH-2) This invention is related to an improved clock mechanism, in particular, a mechanism for use in a clock tower. As will be appreciated by those skilled in the horology art, the parti-cular use for this invention creates unique problems, eg. size, accessibility, accuracy, etc. However, these problems have been overcome by the clock mechanism which is more specifically set forth in the following description and claims. The present mechanism generally includes not only an improved drive mechanism, but also a positive backlash prevention structure as well as means for setting the clock whether or not it is running.

Therefore, one object of this invention is to provide a simple, yet eilicient, clock mechanism to be used particularly in a tower clock.

Another object of this invention is to provide a means for setting a clock in a most expeditious manner regardless of whether the clock is running in a minimum of time.

Another object of this invention is to provide positive and separate backlash prevention means for both hands on the clock.

A further object of this invention is to provide backlash prevention means for an epicyclic gear train.

Other objects of the invention are and will become apparent from the specication herein.

FlG. 1 is a cross-sectional, side view taken along line t-l of FIG. 2 and shows the clock mechanism including the gear trains for both driving and setting the clock hands.

FIG. 2 shows a cross-sectional, fragmentary, backside View of the clock mechanism taken along line 22 of FG. 1.

FIG. 3 is a fragmentary top view of the clock mechanism.

FIG. 4 is an illustrationrof backlash prevention means adapted for use with the pinion and sun gear of an epicyclic gear train.

FIG. 5 is an illustration of backlash prevention means at the point of introducing energy into a gear train.

While the drawings depict a specific clock mechanism, these drawings are considered only illustrative such that the invention of this application is not limited thereto.

Before turning to the details of the drawings, it should be noted that the invention basically comprises two epicyclic gear trains designated as A and B, which trains are used to drive a minute hand C and an hour hand D of a tower clock which includes a clock face E. The gear train B serves the function of a dial train as used in the horology art.

The power train will first be described, i.e. the transmission of energy from synchronous motor l to minute hand C and hour hand D. The synchronous motor ll, which is standard and well known so that further description is not considered necessary, drive shaft 2 to which reducer gear 3 and gear teeth 4 thereof are attached (as best seen in FIG. 2). The gear teeth 4 of reducer gear 3 mesh in a driving relationship with gear teeth 5 of spider gear d which rotates about shaft 'i on cylindrical bearings 3. These bearings d abut the inside cylindrical surface of hub 9 which is at the center of spider gear 8 and which, in turn, abuts thrust bearings 3a at either end. Spider gear S also includes peripheral ICC hubs it) in which cylindrical bearings 2li are located and through which shafts .l2 pass. Main shaft 7 is supported at either end by the clock housing, depicted in FlG. l as housing support elements t3, which elements support bushings id and i5. Bearings i@ and 17 are located inside bushings ltd and t5, respectively. The particular structure surrounding main shaft 7 at the bushing 1S end thereof will be described in more detail later.

Pinned to the end of shafts l2, on one side of spider gear 6, are differential pinions 222 and 24 with gear teeth 25 and 2e, respectively. larger differential pinions 27 and Z8 with gear teeth 29 and 3ft, respectively, are pinned .to the other end of shaft 12. These ipinions 23, 24, 27 and 2S are pinned to the shaft i2 by means of taper pins 3i, as .best shown in FlIG. 1, and are separated from the peripheral hubs it) by thrust bearings lia. The gear teeth 33 of sun gear 32 mesh with gear teeth 29 and 3d of pinions 27' and 2S, respectively, while the hub 34 of sun gear is attached to concentric shaft 35 by means of key 34a and set screw 34h; the shaft 35 also being attached to time setting gear 36 with gear teeth 57 by key it? and set screw ida (see FG. l). As is further evident from FG. l, cylindrical bearings 38 and 3@ separate main shaft '7 from concentric shaft 35 which in turn rides in cylindrical bearing i7 while thrustbearing te is inserted between time setting gear and bushing l5. On the opposite side of spider gear 6, sun gear 41 meshes with teeth Z5 and 26 of pinions 23 and 24, respectively, through its own gear teeth 42 and is attached to main shaft at hub d4- by taper pin 43.

In order to transfer rotational energy from gear train A to gear train B, main shaft '7, driven by attached sun gear di, rotates drive pinion tl with gear teeth 51 since the shaft is attached to said gear by means of taper lpin 52. Drive pin Sil thereby turns intermediate drive gear 53 with gear teeth which results in shaft 55 rotating through the connection there-between by means of ey S6 and set screu 56a (see FIG. l). Attached to an intermediate portion of shaft 55 is pinion 57 with gear teeth SS, said attachment achieved through key 59 and set screw 59a. The shaft 55 is journaled in bearings @il which are to be found in bushings dit supported by the clock housing elements which are depicted here as support elements 62.

The gear teeth 58 mesh with gear teeth 63 of spider gear elfso as to impart rotation to the latter and, consequently, `gear train B. Spider gear 64 is similar to spider gear 6 with the exceptions 4that it is larger, that its center hub 65 is attached to minute hand shaft 66 by key 67a, along with set screws 67h, and that it has four peripheral hubs 67 each with bearings 68 therein and shafts 69 therethrough. rihe minute hand shaft 66 is journaled in bearing itl located in bushing 7i which is supported by the clock housing elements, and which are identied by .the reference numeral 72. Lateral movement of the minute hand shaft 66 is prevented by set screws 73 and groove 74 (see FlG. 4). Minute hand shaft 65 is also journaled in intermediate hearing 75 as Well as bearing 7o and is keyed (not shown) to minute hand C through concentric tubular piece 77 to which said minute hand is attached, for example by welds 75. End caps Si? and Si. provide desired protection and finish while the concentric tubular member '79 of cap titl serves as a spacer. Bolts Stia secure the cap 8@ to minute hand shaft do.

Returning to the periphery of the spider gear 64 and FIG. 1, taper pins connect shafts 68 with differential pinions S6 having gear teeth 87 as well as one larger differential pinion 88 with gear teeth 39 (as shown in the 3 oclock position in FlG. 2). The remaining three pinions 3S are free to rotate on shafts 69 as will be explained later in connection with backlash prevention. It is important to note, however, that each of the pinions S8 has aislar-.ies

a collar 98 pinned to shaft by pins 85. Thrust bearings 96 are inserted between each of the pinions 56 and 88, and the peripheral hubs 67 of spider gear 64. Mesh` ing with the gear teeth 57 of differential pinions S6 (see FIG. 1) are gear teeth 91 of sun gear 92 which is keyed to concentric shaft 93 at 94 (along with set screw 94a). The gear teeth 89 of larger pinions 58 mesh with gear teeth 95 of sun gear 96 which is keyed at 97 to bushing '71 and is therefore fixed. Set screw 97a is used to maintain the xed relationship between sun gear 96 and bushing 71.

Concentric shaft 93 is journaled between bearings '75 and 76 on the inside and bearings 163 and 1114 on the outside and is keyed (not shown) to hour hand D through the concentric tubular piece 165 to which the hour hand is attached, for example by weld 106. Concentric tubular member 107 of head piece 1119 acts as a spacer, and bolts 109a secure piece 169 to hour hand shaft 93. Thrust bearing 108 is inserted between piece 77 and head piece 199 while thrust beariny 110 is inserted between piece 105 and concentric tubular housing 111 which is supported by the clock housing as depicted here by 112. The fins 123, as best shown in FIG. 3, provide structural support for the shafts 66 and 93.

Considering gear train A, again, and specifically the time setting mechanism, a squirrel cage induction motor 119 with drive shaft 120 (see FIG. 3) is used to turn time setting gear 36 through gear 121 and gear teeth 122 thereon with shaft 120 being attached to the latter gear. 1ncluded with the squirrel cage motor 119 is a magnetic brake (not shown) so as to maintain positive control over sun gear 32 through the gear train made of gears 121 and 36.

Positive backlash prevention is independently provided for both the hour hand shaft 93 and the minute hand shaft 66 with FIG. 4 illustrating the principle which applies to the hour hand shaft. In FIG. 4, a fragment of fixed sun gear 96 with teeth 95 along with pinions S6 with gear teeth 87 are shown as pinions 88a and 831': with teeth 89a and 87h, respectively (the reference characters a and b being used for explanatory purposes). As has been mentioned above, the pinions S6 and one pinion 88 along with its collar 98 are pinned to shafts 69 by taper pins 85 (see FIG. 1) while three pinions 88 have been considered free to rotate on shafts 69. Extending from the collars 98 for said three free pinions 68, the collars being pinned to shafts 69 by pins 35, are lugs 113 with tapped holes therein, through which set screws 114 pass and are held in place by nut 115. Thru pins 116 are attached to the pinions 8S (see FIG. 1) and extend axially therefrom in order to abut the set screws 114 as best shown in FIG. 4.

FIG. 4 illustrates, in a simplified form, how this abovedescribed structure, i.e. collars 98, pinions 8S, lugs 113, set screws 114, nuts 115 and pins 116, can be used to prevent backlash in the epicyclic gear train of this invention. Remembering that shafts 69 are rotating with spider gear 64, pinions 88a and $312 thereby rotate counterclockwise as indicated by the arrows through shafts 69 (FIG. 4). Pinion 88a meshes with sun gear 96 through teeth 89a at 117 in a manner which attempts to drive sun gear 96 in a clockwise direction. Note that this face contact at 117 is maintained by set screw 114 abutting against pin 116 of pinion 58a. Pinion 88h, on the other hand, meshes with sun gear 96 at 118 which includes the reverse drive face of pinion teeth 89k, with set screw 114 adjusted to abut pin 116 and thereby maintain the face contact at 115. Thus, pinions 83a and 58h are positively located with respect to shafts 69 as predetermined opposing forces are applied to sun gear 96 at points 117 and 113.

This backlash prevention scheme of FiG. 4 has been adopted by this invention, but in a more sophisticated manner which will be best understood from FIG. 2. Here the pinions of FIG. 4 with their particular gear teeth meshing are shown as pinions 8S at the 12 oclock and 6 oclock positions which pinions are being used to duplicate the opposing forces created by the set screws 114- abutting pins 116 in the pinions 88 to be found in the 3 oclock and 9 oclock positions. In order to facilitate assembly of the epicyclic gear train of this invention, the pinion 88 at 3 oclock is constructed without the lug 113, etc. and is pinned to shaft 69 passing therethrough, thus providing an assembly starting point for establishing the necessary gear teeth relationship between each pinion 88 and sun gear 96. As will be understood, it is not necessary that directly opposite pinions, e.g. 88a and Sb of FIG. 4, form the bases for the opposing forces which result from adjustment of set screws 114, i.e. adjacent pinions could also provide these same opposing forces.

Because every force has an equal and opposite force, the resultant force of each pinion 88 against fixed sun gear 96 is transmitted as a torque through shafts 69 to differential pinions 56 which are themselves pinned to shafts 69 (see FIG. 1). Thus, by locating these pinions 86 so that their teeth 87 mesh with the teeth 91 of sun gear 92 in the particular face to face relationship illustrated by FIG. 4 and at the same time utilizing, at least this last mentioned mesh, the shaft torque created by the resultant force of pinions 33 against the gear teeth 95 of sun gear 96, sun gear 92 will be positively located by pinions 86, thereby preventing backlash in sun gear 92 and error in hour hand shaft 93.

The above-described backlash prevention means may also be used in gear train A as the positive relationship between shafts 12 and pinion 23, 24, 27 and 28 is established by means of pinning each pinion to the shafts after the necessary face contact relationship of gear teeth has been established, i.e. as shown in FIG. 4. While the set screws 114 and thru pins 116 of gear train B could be used in gear train A, the effect of minute and hour hand error created through backlash at this point in the gear train will be nominal, thus eliminating the need for such fine adjustment.

Minute hand error attributed to backlash is similarly prevented through the addition of intermediate idler with gear teeth 126 and idler 127 with gear teeth 128 rotating on shaft 127e (FIG. 2). Since the spider gear s 64, which is directly connected to the minute hand C through shaft 66, is to be positively located, gear teeth 123 of idler 127 contact gear teeth 63 of spider 64 at 139 (FIG. 5) in the same manner as gear teeth 57h of idler S6!) contact gear teeth 91 of sun gear 92 at 118 in FIG. 4. This relationship is established when drive pinion 57, as shown in FIGS. 2 and 5, rotates clockwise so as to drive spider gear 64 at 133 (FIG. 5) in a counterclockwise direction.

Intermediate idler 125 is thereby driven in a counterclockwise direction by means of idler 127 (driven by spider gear 64) since the intermediate idler 125 is positively located between drive pinion 57 and idler 127 by force F on shaft 136 (see FIG. 5). Specifically, this force F will impose intermediate idler 125 upon both drive pinion 57 and idler 127 as the lower faces of teeth 126 (as viewed in FIG. 5) abut pinion teeth 53 at 136 and idler teeth 128 at 137.

Arm 129, which carries intermediate idler 125 on shaft 1519 so as to provide the force F, is pivoted at 131 with the pivot point being connected to the clock housing (exemplified here by the reference numeral 132) and is secured to a horizontal portion of the clock housing (exempiied here by the reference numeral 133) through bolt 134. Set screws 135 (shown only in FIG. 1) maintain as well as provide fine adjustment of the force F on the intermediate idler 125 by abutting against plate 129a at one end while being secured (not shown) in housing support 133 at the other end.

Should it be desired t0 monitor the clock mechanism during normal operation and periods of time setting, a

snags-as Selsyn motor 142 is provided for transmitting the rotation speed of shaft 56 transferred via coupling 141 and cap 140, the latter being attached to the shaft 56. Since Selsyn motors are well known in the art, a detailed description of operation will not be made except to point out that it is possible to use a second Selsyn motor as a receiver for the information transmitted by 142 and thereby reproduce the clock motion at a location apart from the clock.

In operation, the synchronous motor 1 drives shaft 2 and consequently reducing gear 3 which meshes with spider gear 6 for rotation. thereof. Spider gear 6 rotates about shaft 7 on bearings S and further causes differential pinions 23 and 24 to rotate about sun gear 41 as well as causing differential pinions 27 and 28 to rotate about sun gear 32. During normal operation, i.e. when the hands are not being set, sun gear 32 is held stationary through control of squirrel cage motor 119 and the magnetic brake while the differential gear sizes permits sun gear 41 to, itself, rotate which imparts motion to shaft 7 attached thereto. Shaft 7 turns drive pinion 50 which transfers its motion to intermediate drive gear 53 keyed to shaft 56. Also keyed to shaft 56 is drive pinion 57 which meshes with spider gear 64 thus completing the transfer of energy from gear train A to gear train B.

The rotation of spider gear 64 is divided two ways in gear train B. First, key 67a directly connects center hub 65 of spider gear 64 with minute hand shaft 66 so that the rotating speed of spider gear 64 is also that of minute hand C. Secondly, sun gear 94 turns hour hand shaft 93 which is directly connected to hour hand D. The sun gear 92, itself, rotates as a result of the circular motion of differential pinions 86 and S8 about hub 65 of spider gear 64 combined with the rotation of differential pinions 86, resulting from the rotation of differential pinion 8S on fixed sun gear 96.

When it is necessary to set the clock hands C and D, the magnetic brake associated with squirrel cage motor 119 is released causing gear 121 to rotate time setting gear 36. Since the latter gear is keyed to concentric shaft 35, which is in turn keyed to sun gear 32, the net result is increased rotational speed for sun gear 32 so as to speed up pinion 27 `and/ or 28, as the case may be. This increased speed is transmitted through shaft 12 to the normal power train of gear trains A and B, previously described. As will be noted, this structure permits setting of the clock hands while the ordinary clock drive mechanism continues to function. It should also be noted that by using a reversible squirrel cage motor, the clock hands may be moved forward or backward. In an actual reduction to practice of this clock mechanism, the hands of the clock can be set ahead one hour in a time interval of 59 seconds and can be retarded one hour in a time interval of 6l seconds.

Thus, it is evident that the above-described invention is a most significant contribution to the art.

We claim:

1. In a clock mechanism for a tower type clock having an hour hand shaft and a minute hand shaft combined with a dial train which supplies substantial torque to said shafts, said dial train comprising,

(a) drive means for a spider gear means which gear means is attached at a center hub thereof to said minute hand shaft,

(b) said spider gear means comprising at least one gear shaft hub near the periphery thereof,

(c) gear shaft means located in each gear shaft hub and free to rotate therein,

(d) first and second differential pinion means attached to each gear shaft,

(e) first sun gear means attached to said hour hand shaft which is concentric with said minute hand shaft, and

(f) a second sun gear means attached to a xed shaft concentric with said minute hand shaft,

(g) said first and second differential pinion means in rotatable contact with said first and second sun gear means respectively.

2. In a clock mechanism for a tower type clock having an hour hand shaft and a minute hand shaft combined with a dial train which supplies substantial torque to said shafts, said dial train comprising,

(a) drive means for a spider gear means which is attached at a center hub thereof to said minute hand shaft,

(b) said spider gear comprising a plurality of gear shaft hubs near the periphery thereof,

(c) gear shaft means located in each of said gear shaft hubs and free to rotate therein,

(d) pinion means attached to each gear shaft with the axis of said pinion means being parallel to the axis of said minute hand shaft,

(e) said pinion means on one side of said spider gear means being smaller in diameter than those pinion means on the other side of said spider gear means,

(f) first sun gear means attached to said hour hand shaft which is concentric with said minute hand shaft, and in rotatable contact with said smaller pinion means, and

(g) a second sun gear means attached to a fixed shaft in axial alignment with said minute hand shaft, and in rotatable contact with said larger pinion means.

3. In combination with the clock mechanism of claim l, means to prevent backlash in said spider gear, and hence said minute hand shaft, comprising:

(a) pinion drive means intermediate said drive means and said spider gear means,

(b) idler gear means meshing with said spider gear means,

(c) intermediate idler gear means which mesh with both said pinion drive means and said idler gear means, and

(d) means to urge said intermediate idler gear means against said pinion drive means and said idler gear means so as to prevent backlash in said spider gear.

4. In combination with the clock mechanism of claim l, means to prevent backlash in said first sun gear means, and hence said hour hand shaft, comprising:

(a) lug means extending radially from a collar of said second differential pinion means contacting said second sun gear which pinion means are free to rotate on said gear shaft with said collar being secured to said gear shaft,

(b) said lug means including a bore transverse to the axis of said pinion means,

(c) pin means attached to said second differential pinion means and extending axially therefrom, and

(d) set screw means rotatively secured in each lug hole and abutting the pin means thereof for positively locating said differential pinion means with respect to said gear shaft means and thereby preventing backlash in said first sun gear.

5. In combination with the clock mechanism of claim l, means to prevent backlash in both said spider gear, and hence said minute hand shaft, as well as said first sun gear means, and hence said hour hand shaft comprising:

(a) pinion drive means intermediate said drive means and said spider gear means,

(b) idler gear means meshing with said spider gear means,

(c) intermediate idler gear means which mesh with both said pinion drive means and said idler gear means,

(d) and means to urge said intermediate idler gear means against said pinion drive means and said idler gear means so as to prevent blacklash in said spider gear means,

(e) lug means extending radially from a collar of said second differential pinion means contacting said second sun gear which pinion means are free to ro- 7 tate on said gear shaft with said collar being secured to said gear shaft,

(f) said lug means including a bore transverse to the axis of said pinion means,

(g) pin means attached to said second differential pinion means and extending axially therefrom, and

(h) set screw means rotatively secured in each lug hole and abutting the pin means thereof for positively locating said differential pinion means with respect to said gear shaft means and thereby preventing backlash in said first sun gear.

6. in combination with the clock mechanism of claim l, a time setting mechanism with a time setting shaft means comprising:

(a) second drive means for a second spider gear means which gear means rotates freely on a second drive shaft means through a center hub thereof,

(b) said second spider gear means comprising at least one gear shaft hub near the periphery thereof,

(c) second gear shaft means located in each gear shaft hub of said second spider gear means and free to rotate therein,

(d) third and fourth differential pinion means attached to each of said second gear shaft means,

(e) third sun gear means attached to said drive shaft means and engaging said third differential pinion means,

() fourth sun gear means attached to said time setting shaft means concentric with said drive shaft means and engaging said fourth differential pinion means,

(g) time setting means connected to said time setting shaft means so as to permit rotation of said time setting shaft and said fourth sun gear only during periods of time setting, and

(l1) intermediate drive means connecting said second drive shaft means and said dial train.

7. In the combination of claim 6.

(a) said second drive means comprising a synchronous motor means and an attached reducer gear means which drives said second spider gear means, and

(b) said time setting means comprising a squirrel cage motor means and associated brake means.

8. In combination with the mechanism of claim 3, a time setting mechanism with a time setting shaft means comprising:

(a) second drive means for a second spider gear means which second gear means rotates freely on a drive shaft means through a second center hub thereof,

(b) said second spider gear means comprising at least one gear shaft hub near the periphery thereof,

(c) second gear shaft means located in each gear shaft hub of said second spider gear means and free to rotate therein,

(d) third and fourth differential pinion means attached to each of said second gear shaft means,

(e) third sun gear means attached to said drive shaft means and engaging said third differential pinion means,

(f) fourth sun gear means attached to said time setting shaft means concentric with said drive shaft means and engaging said fourth differential pinion means,

(g) time setting means connected to said time setting shaft means so as to permit rotation of said time setting shaft and said fourth sun gear only during periods of time setting, and

(h) intermediate drive means connecting said second drive shaft means and said dial train.

9. In combination with the mechanism of claim 4, a time setting mechanism with a time setting shaft means comprising:

(a) second drive means for a second spider gear means which gear means rotates freely on a second drive shaft means through a center hub thereof,

(b) said second spider gear means comprising at least one gear shaft hub near the periphery thereof,

(c) second gear shaft means located in each gear shaft hub of said second spider gear means and free to rotate therein,

(d) third and fourth differential pinion means attached to said second gear shaft means,

(e) third sun gear means attached to said drive shaft means and engaging said third differential pinion means,

(f) fourth sun gear means attached to said time setting shaft means concentric with said drive shaft means and engaging said fourth differential pinion means,

(g) time setting means connected to said time setting shaft means so as to permit rotation of said time setting shaft and said fourth sun gear only during pe` riods of time setting, and

(lz) intermediate drive means connecting said second drive shaft means and said dial train.

l0. ln combination With the mechanism of claim 5, a time setting mechanism With a time setting shaft means comprising:

(a) second drive means for a second spider gear means which gear means rotates freely on a second drive shaft means through a center hub thereof,

(b) said second spider gear means comprising at least one gear shaft hub near the periphery thereof,

(c) second gear shaft means located in each gear shaft hub of said second spider gear means and free to rotate therein,

(d) third and fourth differential pinion means attached to said second gear shaft means,

(e) third sun gear means attached to said drive shaft means and engaging said third differential pinion means,

(f) fourth sun gear means attached to said time setting shaft means concentric with said drive shaft means and engaging said fourth differential pinion means,

(g) time setting means connected to said time setting shaft means so as to permit rotation of said time set- `ting shaft and said fourth sun gear only during periods of time setting, and

(l1) intermediate drive means connecting said second drive shaft means and said dial train.

References Cited by the Examiner UNITED STATES PATENTS 2,026,368 12/35 Warren 58-34 2,103,259 12/37 Hitt 74-675 2,519,042 8/50 Granberg et al 90-21 2,966,806 l/61 Luning 74-409 2,968,965 l/6l Swanson et al. 74-409 FOREIGN PATENTS 815,777 4/ 37 France.

LEO SMILOW, Primary Examiner. 

1. IN A CLOCK MECHANISM FOR A TOWER TYPE CLOCK HAVING AN HOUR HAND SHAFT AND A MINUTE HAND SHAFT COMBINED WITH A DIAL TRAIN WHICH SUPPLIES SUBSTANTIAL TORQUE TO SAID SHAFTS, SAID DIAL TRAIN COMPRISING, (A) DRIVE MEANS FOR A SPIDER GEAR MEANS WHICH GEAR MEANS IS ATTACHED TO A CENTER HUB THEREOF TO SAID MINUTE HAND SHAFT, (B) SAID SPIDER GEAR MEANS COMPRISING AT LEAST ONE GEAR SHAFT HUB NEAR THE PERIPHERY THEREOF, (C) GEAR SHAFT MEANS LOCATED IN EACH GEAR SHAFT HUB AND FREE TO ROTATE THEREIN, (D) FIRST AND SECOND DIFFERENTIAL PINION MEANS ATTACHED TO EACH GEAR SHAFT, (E) FIRST SUN GEAR MEANS ATTACHED TO SAID HOUR HAND SHAFT WHICH IS CONCENTRIC WITH SAID MINUTE HAND SHAFT, AND (F) A SECOND SUN GEAR MEANS ATTACHED TO A FIXED SHAFT CONCENTRIC WITH SAID MINUTE HAND SHAFT, 